Medical Writing  

Travel Writing

Creative Writing 

Cholesterol levels in the blood

Once cholesterol is absorbed through the small intestine, it enters the blood circulation and is then referred to as plasma cholesterol. Plasma cholesterol is derived from both endogenous and exogenous cholesterol. The level of cholesterol in the bloodstream is affected by the rate of:

·         Cholesterol biosynthesis

·         Absorption of dietary cholesterol

·         Absorption of cholesterol from bile

·         Removal of cholesterol from the circulation

________________________________________________________

Hormone Replacement Therapy

Hormone replacement therapy (HRT) is used to relieve the acute symptoms of menopause and to address the long-term effects of estrogen deficiency, including osteoporosis.  The indications for HRT may include treatment of the following conditions associated with menopause:

§           treatment of vasomotor symptoms

§           treatment of vulvar and vaginal atrophy

§           prevention of osteoporosis

The hormones used in combined HRT are an estrogen and a progestin.  Progestins are used in women with an intact uterus to reduce the risk of endometrial hyperplasia — a condition that has been associated with endometrial cancer.

_______________________________________________________________________

Clinical Evaluation

The clinical evaluation of a patient with suspected cancer development involves eliciting the following: a thorough family history of the disease, repeated exposure to carcinogens, or the physical manifestations of cancer. Appropriate measures, such as careful physical examinations and diagnostic screening tests, are used to detect cancer in its early stages.

The American Cancer Society has identified 7 warning signs of cancer, which can be retained using the acronym CAUTION:

·         C: Change in bowel or bladder habits

·         A: A sore that does not heal

·         U: Unusual bleeding or discharge

·         T: Thickening or lump in breast, testicles, or elsewhere in the body

·         I: Indigestion or difficulty in swallowing

·         O: Obvious change in wart or mole

·         N:  Nagging cough or hoarseness

Reference:

Mendelsohn J. Principles of Neoplasia. Isselbacher KJ, Braunwald E, Wilson JD, Martin NB, Fauci AS, Kasper DL, eds. Harrison’s Principles of Internal Medicine. 13^th ed. New York, NY: McGraw-Hill; 1994:1823-24.

Diagnostic imaging

If the clinical evaluation suggests that a patient may be at risk of developing cancer, diagnostic imaging studies can help confirm the diagnosis, and determine the extent of the disease prior to treatment.

Diagnostic imaging studies are used for the following purposes:

·         Screening for cancer: Checking for suspicious or abnormal areas that might be cancerous

·         Diagnosing and staging: Locating the cancer in the body, and determining if it has spread and how much is present

·         Guiding cancer treatments: Making cancer treatments less invasive by using imaging techniques to focus treatment on the tumors

·         Determining treatment efficacy: Verifying the size or consistency of the tumor during treatment

·         Monitoring for cancer recurrence: Checking if a previously treated cancer has returned or has spread to other body parts

The most common types of diagnostic imaging studies are:

·         X-ray imaging

·         CT scans

·         Nuclear imaging (radiolabeled antibodies and PET scans)

·         MRI

·         Ultrasound

·         Colonoscopy

X-ray imaging

X-ray imaging produces a two-dimensional image of the body on a film after X-ray beams are radiated toward the patient’s body.  Calcium in bones has the highest rate of absorption, therefore bones appear white on the film. Dense masses of cells, such as cancer cells, can also be detected using X-ray imaging.

CT scans

A Computed Tomography scan (CT scan or CAT scan) uses X-rays to produce a three-dimensional image of the body. A computer collects the information on how much of the X-rays are passing through the body. Thin slices (3.5 mm each) of the body are produced, like thinly sliced bread, creating a composite of the body. The three-dimensional quality of the CT scan allows a radiologist to not only determine the location of the tumor, but also its depth within the body.

Conventional and spiral CT scans exist. Conventional scans take pictures of the body in slices. Spiral scans take continuous pictures of the body in a spiral motion, therefore eliminating gaps in the collected pictures.

Nuclear imaging

Nuclear imaging uses radioactive substances that are linked to compounds used by the cells in the body or compounds that recognize cancerous cells. Special detection equipment tracks the radioactive substances in the body and locates the area where they are most concentrated. The two main areas of nuclear imaging are radiolabeled antibodies and PET scans.

Radiolabeled antibodies

Antibodies are linked a radioactive substance. The antibody portion of this compound will stick to any cancerous cells if they are present.

PET scan

In Positron Emission Tomography (PET) scan, a radioactively linked substance normally used by the body is injected into the patient. Areas of high metabolism can be detected, such as areas that use more resources such as glucose, blood or oxygen. Tumor cells are usually involved in areas of high metabolism because of their uncontrolled proliferation and requirements for more nutrients and resources.

MRI

Magnetic Resonance Imaging (MRI) uses radio frequency waves within a strong magnetic field produced by the MRI machine in order to allow cells to emit their own radio frequency. Different cells emit a more or less intense signal that is based on their chemical makeup. Tumor cells also emit their own frequency. MRI scans produce a three-dimensional image of sections of the body. MRI is usually more sensitive than a CT scan or an X-ray.  MRI is an established technique used for the imaging of organs and tissues including the heart, the brain, bone marrow, cartilage, and the abdomen.

Ultrasound

Ultrasound technique uses sound waves whose frequency is far beyond the capacity of the human ear. A device called transducer gives off sound waves that are then reflected back from organs and tissues. The image of the body is then reflected on a screen.

Ultrasound is used to look for tumors, and can help guide physicians during biopsies or laser therapy.

Colonoscopy

Conventional colonoscopy uses a device called a sigmoidoscope to screen for tumors or polyps in the colon. The colon is the lower part of the gastrointestinal tract. A sigmoidoscope is a thin tube with light used to view inside the colon. A newer, more appealing version is the virtual colonoscopy. A spiral CT scan is taken of the gastrointestinal area, and then the computer creates a composite image of the patient’s colon. However, the patient must still undergo insertion of a probe to push air into the colon. Clinical trials still have not determined whether the efficacy of virtual colonoscopy is equivalent to conventional colonoscopy.

Reference:

Mendelsohn J. Principles of Neoplasia. Isselbacher KJ, Braunwald E, Wilson JD, Martin NB, Fauci AS, Kasper DL, eds. Harrison’s Principles of Internal Medicine. 13^th ed. New York, NY: McGraw-Hill; 1994:1824.

Cancer imaging. National Cancer Institutes. Available at: http://www.cancer.gov/templates/page_print.aspx?viewid=bdb4c09c-d1ec-4dd7-a377-ad645854daa3#c8c338fc-fb7d-43f7-a5e2-220dd8c07016 Accessed March 26, 2002

Laboratory studies

A number of laboratory tests are available to diagnose cancer. These tests are generally classified into 5 categories:

·         Tissue sampling

·         Immunocytochemistry

·         Molecular diagnosis

·         Flow cytometry

·         Tumor maker detection

Tissue sampling

Tissue sampling can be used to obtain tissues for histological and cytological evaluation. This means that tissue samples are screened for cancerous or pre-cancerous cells.

There are 3 methods of tissue sampling:

·         Biopsy or excision: Removal of a sample of the lesion

·         Fine-needle aspiration: Aspiration of cells and their surrounding fluid with a fine needle, used to assess tumors of the breast, thyroid, and lymph nodes

·         Cytological (Pap) smear: Scraping of the cervix for cells, mostly used to diagnose cervical cancers

Immunocytochemistry

Immunocytochemistry is the study of cell surface markers or other products that characterize malignant cells. This technique helps determine the origin of a neoplasm.

Specific antibodies are directed against cell-surface receptors, tissue specific or organ specific markers, or cell-specific products with the goal of identifying these.

Immunocytochemistry can be used for the following purposes:

·         Categorization of undifferentiated malignant tumors

·         Categorization of leukemias and lymphomas

·         Determination of site of origin of metastatic tumors

·         Detection of molecules of prognostic or therapeutic significance

Molecular diagnosis

A variety of molecular techniques are used to detect the presence of specific chromosomal alterations or other genetic mutations. The molecular assessment of a neoplasm can be used to detect abnormal growths that are malignant, to determine the prognosis of a malignant neoplasm, to detect residual disease following cancer treatment, and to detect an individual’s predisposition to developing cancer.

Flow cytometry

Flow cytometry is a technique that assesses unique characteristics of cells. Flow cytometry can measure the expression of cell surface antigens or the DNA content of a cell sample. This technique permits the detection of malignant cells that express abnormal surface proteins or abnormal amounts of DNA (chromosomal additions or deletions).

Tumor marker detection

Tumor makers are molecules expressed by tumors such as cell surface proteins, cytoplasmic proteins, enzymes, and hormones. These substances are usually detected in the plasma or other body fluids, where an abnormal expression characteristic of particular tumors. Tumor marker detection is primarily used to confirm the diagnosis of cancer.

Reference:

Chapter 8. Neoplasia. In: Cotran RS, Kumar V, Collins T, eds. Pathologic Basis of Disease. 6^th ed. Philadelphia, PA: Saunders; 1999: 322-325.